The objective of this research proposal is to obtain information on the endocrine events which regulate function and regression of the corpus luteum and to understand the processes by which this control is achieved. Specifically, it is planned to extend studies in areas where significant regulation and control appears to exist based upon the results obtained in the past two years of research support. We propose to examine: 1. The mechanism of PGF2 alpha- induced inactivation of LH dependent adenylate cyclase with emphasis on the role of calcium and phospholipids. 2. The mechanism of control and regulation of gonadotropin uptake by the corpus luteum in vivo. 3. Possible mediation of hormone dependent blood flow in the ovary and uterus by prostaglandins and thromboxane. 4. The ontogeny of LH receptor turnover in the corpus luteum. This research will involve physiological, morphological and biochemical analysis of organ, cellular, and subcellular sites of hormone and hormone receptor regulation of cell function. Although the experiments will depend primarily upon the rat model, rabbits, guinea pigs will also be used and in selected in vitro studies, human luteal tissue. With these approaches we may increase our understanding of endocrine and cellular control processes and perhaps identify discrete targets for development of pharmacological agents for induction of luteal regression and fertility control.